The electrode reactions of Fe(CN)63− and Fe(CN)64− ions studied at temperatures below the melting point of stoichiometric electrolytes

Cyclic Voltammetry for Accurate Icing Detection on Simulated Aircraft Surfaces

Icing and ice accretion on aerodynamically critical surfaces of an aircraft increase drag, reduce lift, and raise stalling speed, which pose significant safety hazards to aircraft while in flight. Icephobic coatings have been intensively investigated by the Canadian and global aerospace industries for passive ice protection. Nevertheless, effective icephobic coatings suitable for aerospace applications are far from ideal. Ice protection of an aircraft still relies on active ice protection systems based on heating, mechanical expulsion, and deicing fluids, which are heavy-weight, power-intensive, and unfriendly to the environment. To address these challenges, rapid and accurate detection of icing is highly desirable to activate these ice protection systems only when needed. To this end, cyclic voltammetry was used for the first time to detect the initiation of icing on aircraft surfaces with or without icephobic coatings. In this study, a water droplet was sandwiched between a screen-printed electrode and a simulated aircraft surface. Cyclic voltammograms were then collected as the temperature was slowly decreased until the droplet froze to form ice. A sharp spike in faradaic current was recorded in the voltammograms during the phase transition, suggesting a switch in the mass transfer mechanism from diffusion to a surface-confined pathway. This electrochemical signal could then be used to precisely indicate the onset of icing. The developed sensing method shows potential in icing detection to manage active ice protections and ameliorate icing risks in the aerospace and aviation industries.

Wash-free photoelectrochemical DNA detection based on photoredox catalysis combined with electroreduction and light blocking by magnetic microparticles

To obtain a sensitive, wash-free photoelectrochemical biosensor based on electron mediation between an electrode and a photoredox catalyst (PC) label, unavoidable O₂-related reactions should have no effect or be beneficial, and the rate of electron mediation should depend on the distance between the PC label and electrode. A wash-free photoelectrochemical biosensor that (i) combines photoredox catalysis of a PC label with electrochemical reduction of an electron mediator, and (ii) uses a light-blocking multilayer of magnetic microparticles was developed. O₂ participates as an electron acceptor in photoredox catalysis; thus, increasing rather than decreasing the electrochemical signal. Upon photoirradiation from the opposite side of a transparent indium tin oxide (ITO) electrode in contact with the solution, the light intensity in the solution is sharply decreased by the light-blocking multilayer, which increases the contribution of affinity-bound PC labels on the ITO electrode to the electrochemical signal compared to that of unbound PC labels in solution. Utilizing eosin Y (EY^2-) and Fe(CN)₆^4- as the PC and electron mediator (i.e., electron donor), respectively, enabled rapid redox cycling based on photoredox catalysis combined with electroreduction. The cathodic charge is mainly related to electron transfer from Fe(CN)₆^4- to excited EY^2- (Type I photosensitization), rather than energy transfer from excited EY^2- to O₂, which generates ¹O₂ (Type II photosensitization). The developed detection scheme was applied to wash-free detection of a model target DNA. Detection limits of ∼200 pM were obtained in both phosphate-buffered saline and serum without washing. The developed scheme enables simple photoelectrochemical detection.